app\auth\forms(3).py

#...

class ChangePasswordForm(FlaskForm):
    old_password = PasswordField('Old password', validators=[DataRequired()])
    password = PasswordField('New password', validators=[
        DataRequired(), EqualTo('password2', message='Passwords must match.')])
    password2 = PasswordField('Confirm new password',
                              validators=[DataRequired()])
    submit = SubmitField('Update Password')


class PasswordResetRequestForm(FlaskForm):
    email = StringField('Email', validators=[DataRequired(), Length(1, 64),
                                             Email()])
    submit = SubmitField('Reset Password')


class PasswordResetForm(FlaskForm):
    password = PasswordField('New Password', validators=[
        DataRequired(), EqualTo('password2', message='Passwords must match')])
    password2 = PasswordField('Confirm password', validators=[DataRequired()])
    submit = SubmitField('Reset Password')


class ChangeEmailForm(FlaskForm):
    email = StringField('New Email', validators=[DataRequired(), Length(1, 64),
                                                 Email()])
    password = PasswordField('Password', validators=[DataRequired()])
    submit = SubmitField('Update Email Address')

    def validate_email(self, field):
        if User.query.filter_by(email=field.data.lower()).first():
            raise ValidationError('Email already registered.')